Methods for dewatering material in a centrifugal machine



un 6, 9 P. VAN RIEL METHODS FOR DEWATERING MATERIAL IN A CENTRIFUGAL MACHINE Filed Nov. 12, 1953 INVENTOK PIET'EK VAN RIEL United States Patent METHODS FOR DEWATERING MATERIAL IN A CENTRIFUGAL MACHINE Pieter Van Riel, Delft, Netherlands, assignor to Machinefabriek Reineveld N. V., Delft, Netherlands, a company of the Netherlands Application November 12, 1953, Serial No. 391,681 3 Claims. (Cl. 210-69) This invention relates to a method for dewatering material in a centrifugal machine and a machine for carrying out such method, which may comprise a distributing drum provided with blades or flights, a perforated inner drum concentrically surrounding said distributing drum and having also blades, a perforated outer drum concentrically surrounding said inner drum and said inner drum being adapted to rotate with an angular speed slightly differing from that of the distributing drum and that of the outer drum.

When treating in a centrifugal machine material comprising in addition to coarser particles also finer particles, such as fine grained coal and crystallized masses, the drawback arises that together with the liquid also fine material escapes through the screen wall of the drum.

The invention has for its object to avoid said loss of fine material. According to the invention the material to be treated is introduced into the perforated inner drum and coarser particles of the same material are introduced into the outer drum in such a manner that said coarser particles form a displacing filtering layer on the inner side of the outer drum, the dewatered fractions being discharged together. The finer particles passed through the perforated wall of the inner drum are arrested in the coarser layer formed on the inner side of the outer drum, so that said layer serves as a filter for the finer material. Moreover an efficient dewatering of the material is secured as the outer drum may be provided with a relatively coarse-mesh screen wall.

According to the invention said method is preferably carried out by means of a centrifugal machine having a conical inner drum and a conical outer drum each widening towards the discharge end.

The invention will be further described with reference to the accompanying drawing showing half a sectional elevation of a centrifugal machine according to the invention.

The perforated inner drum 1 is provided with conveying blades 2 at its outer side and secured on a shaft 3. Drum 1 is surrounded by a drum 4 having also a perforated circumferential wall and being connected to the distributing drum 6 by means of spokes 5 and provided with blades 7. The drums 4 and 6 are secured to a hollow shaft 8 enclosing the shaft 3 of drum 1. The shafts 3 and 8 are driven by a shaft through the medium of a pair of gear wheels 16 and 17 respectively and in such a manner that the drums 4 and 6 rotate with an angular speed slightly differing from that of the drum 1.

The coarser fraction of the material to be treated is supplied by the hopper 10 mounted on the stationary housing 9 and is caught by vanes 11 rotating together with the drum 1 so that the material is accelerated and enters the space between the drums 1 and 4 in order to be dewatered on the screen wall of the drum 4 and displaced downwards by the blades 2.

The finer fraction of the material is supplied by the hopper 12 and caught by the blades 13 arranged on the hub 14, said blades introduce the material into the inner drum 1 so that it is dewatered on the inner side of the screen wall of said drum and discharged downwards by the conveying blades 7 of drum 6. Both the finer frac- 'ice tion and the coarser fraction are discharged together in a common space 18 so that the finer material joins the coarser material. The fine particles escaping through the screen wall of drum 1 are further dried on the coarser layer displacing on the inner side of drum 4, whereby said layer acts as a filter, so that also the finest particles are arrested and a liquid as clean as possible is discharged, whereas still an efiicient rate of dewatering is obtained.

By way of example it may be stated that the centrifugal machine described above the largest diameter of the outer drum 4 may be 1060 mm. and its speed may be 500 revolutions per minute. The number of revolutions of the inner drum 1 may differ from that of the outer drum by 1 to 5%. Into the outer drum fine grained coal and into the inner drum a slurry of coal dust consisting of particles smaller than .25 mm. may be introduced in equal quantities by weight. The blades 2 leave a clearance of about 3 mm. with respect to the inner side of the drum 4 and the blades 7 leave a clearance of about .1 mm. with respect to the inner side of drum 1. The screen wall of drum 1 may consist of rustless steel plate having a thickness of .5 mm. and perforations of a diameter of .18 mm. The screen wall of drum 4 may consist of steel plate having a thickness of 2 mm. and perforations of a somewhat larger size.

Not only fine grained coal and a slurry of coal dust but also crystallized salt solutions such as ammonium sulfate, borax, potassium chloride, sodium chloride, potassium sulfate, calcium formiate, fine grained sodium carbonate and sodium sulfate may be treated in the centrifugal machine, the particles of different size being then obtained by varying the crystallizing process. Also finely divided substances such as pancreas glands, acetate cellulose and naphthalene may be dried in the centrifugal machine.

What I claim is:

1. A method for dewatering material in a centrifugal machine provided with a perforated inner drum and a perforated outer drum concentrically surrounding the inner drum and rotatable with an angular speed slightly difiering from that of the inner drum, which consists in introducing into the inner drum the material to be dewatered, introducing into the outer drum particles of the same material of a larger size, the material forming a layer on the inner walls of both drums, displacing both said layers towards the discharge end of the drums, and discharging both said layers together.

2. A method for dewatering material which consists in introducing the material to be dewatered into an inner receptacle of two concentrically arranged perforate receptacles, which are adapted to be rotated at different speeds and which have a discharge end, introducing into the other receptacle particles of the same material of a larger size, the material forming a layer on the inner walls of both receptacles when the receptacles are rotating, displacing both said layers toward the discharge end of the receptacles, and discharging both said layers together.

3. A centrifugal machine comprising a distributing drum provided with blades, a perforated inner drum concentrically surrounding said distributing drum and having also blades, a perforated outer drum concentrically surrounding said inner drum, said inner drum being adapted to rotate with an angular speed slightly differing from that of said distributing drum and that of said outer drum, said inner drum and said outer drum having a common discharge end and each having a conical shape widening towards said discharge end.

References Cited in the file of this patent UNITED STATES PATENTS 1,334,023 Elmore Mar. 16, 1920 1,634,868 Elmore July 5, 1927 2,156,253 Clark Apr. 25, 1939 

1. A METHOD FOR DEWATERING MATERIAL IN A CENTRIFUGAL MACHINE PROVIDED WITH A PERFORATED INNER DRUM AND A PERFORATED OUTER DRUM CONCENTRICALLY SURROUNDING THE INNER DRUM AND ROTATABLE WITH AN ANGULAR SPEED SLIGHTLY DIFFERING FROM THAT OF THE INNER DRUM, WHICH CONSISTS IN INTRODUCING INTO THE INNER DRUM THE MATERIAL TO BE DEWATERED INTRODUCING INTO THE OUTER DRUM PARTICLES OF THE SAME MATERIAL OF A LARGER SIZE, THE MATERIAL FORMING A LAYER ON THE INNER WALLS OF BOTH DRUMS, DISPLACING BOTH SAID LAYERS TOWARDS THE DISCHARGE END OF THE DRUMS, AND DISCHARGING BOTH SAID LAYERS TOGETHER 